In our British Patent Specifications Nos. 1601917 and 1601918 there is disclosed a form of ammunition which comprises a hollow outer casing, a pressure cylinder within the casing, valve means at one end of the cylinder, a missile located in a mouth at a nose end of the casing, the pressure cylinder being slidable within the casing to cause the valve means to open and permit compressed air, contained in the cylinder, to flow from the cylinder to the mouth of the casing to expel the missile. The ammunition could be recharged with compressed air and a new missile, so as to be readily re-useable.
The ammunition was designed for use in a firearm, with temporary modification of the latter to provide a barrel sleeve and a blunt firing pin, or for use in a similar weapon permanently adapted only to accept such ammunition to enable missiles of air gun pellet form to be employed for qualification as an air gun and not as a firearm under the laws of certain countries.
While such ammunition was effective when initially tested in particular guns under laboratory conditions, further trials revealed many disadvantages some of which could not be overcome by prolonged development of, and engineering modifications to, the ammunition and the guns. (As a result, our alternative form of practice ammunition, decribed in our British Patent Specification No. 2044896A, was developed for production and is now in use). Said disadvantages included wide variations in the accuracy and velocity of missiles fired under identical conditions using apparently identical ammunition, difficulties in recharging and reloading the ammunition, premature discharge risks, and incompatibility of the gun/ammunition combination with the laws of certain countries. Further, said developments and engineering modifications, while overcoming or reducing some disadvantages, would have been excessively expensive if put into production.
What is still needed is, as mentioned in said Specifications Nos. 1601917 and 1601918, means enabling persons to practice shooting, which offers a combination of the advantages of standard air guns with the advantages arising from using cartridge ammunition, without the costs and hazards involved in the use of explosive propellants.